Operating mechanism



Sept. 27, 1938.

c. THUMl M 3 OPERATING MECHANISM Filed April 30, 1937 .30 Inventor: CoriThu i'm,'

by v His Attorney.

Patented Sept. 27, 1938' OFFIE OPERATING MECHANISM Carl Thumim,Lansdowne, Pa, assignor to General Electric Company, a corporation ofNew York Application April 30, 1937, Serial No. 139,903

9 Glaims.

.10 rugged in construction.

In the application of cam-operating mechanisms of the above describedcharacter to means such as, for example, a circuit breaker operablebetween open and closed circuit positions, it is 3 desirable that thecam assume a predetermined angular position at the beginning of theclosing operation with respect to the means to be operated. This isparticularly important where the circuit breaker mechanism is of thetrip-free type wherein a collapsible linkage normally maintained in thethrust-transmitting position by tripping means coacts directly with themotor-driven cam. The operating or Working stroke in this case is thecircuit-closing stroke, at the end of which the motor is automaticallydeenergized.

Since the closing stroke must be positive and fast a comparatively largeamount of kinetic en ergy is stored in the rotating mass at the end ofthe stroke.

High speed braking means has been proposed for stopping the cam but,since in many cases instant dissipation of the large amount of kineticenergy is impractical and may even cause damage to the mechanism, thecam, in accordance with the present invention, is permitted toovertravel and the kinetic energy is gradually dissipated in frictionand by other means. Further, in accordance with my invention the cam isautomatically centered or restored to the desired predetermined angularposition prior to another operating stroke, thereby permitting a highspeed operating stroke uniform in time.

My invention will be more fully set forth in r the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

Referring to the drawing Fig. 1 is a partly diagrammatic view of acam-operating mechanism embodying the present invention in the open,reset position in readiness for a working stroke; Fig. 2 is a partialView of the mechanism in the closed position, i. e., at the end of aworking stroke, and Fig. 3 is a View similar toFig. 1 showing a modifiedform of my invention.

The operating mechanism illustrated by Fig. 1 comprises an electricmotor I operatively connected through suitable gearing 2 and any operat-5 ing shaft diagrammatically indicated at 3 to a r0- tatable cam t. Thecam A is provided with a suitably designed operating face 4 and issecured to the shaft 3 so as to be rotated in a counterclockwisedirection as viewed upon energization 10 of the motor I.

' The means to be actuated is generally indicated at 5 and may comprisethe operating rod of an electric circuit breaker, for example. The rod 5is shown in the open position and is operatively ;l related to the camthrough a collapsible thrust transmitting linkage indicated at n. Thelinkage ,is normally held in thrust-transmitting position by a trippingmeans indicated at I. With the linkage in the open and reset positionshown, a 20 revolution of the cam 4 is effective to cause a workingstroke, the completion of which is indicated by the linkage andoperating rod in the dotted line positions. I

The thrust-transmitting structure can be of 25 7 any suitable design,the one shown by way of example comprising a main toggle 89 including aroller It which coacts with the operating face 4 of the cam. The togglelink 8 is pivotally connected at one end at H to a guide link l2 hav- 3ning a fixed pivot 13, and the toggle link 9 is pivotally connected at Itto a lever l5 which is in turn pivotally connected at IE to the breakeroperating rod 5. The pivot ll of the toggle link 8 is normally heldfixed by the tripping means I, .35 so that when the toggle 8-9 isstraightened at its knee joint ll by the cam, the lever i5 is rotatedabout its fixed pivot It in a clockwise direction to lower the operatingrod 5.

The tripping means 1 specifically comprises a 4n tripping toggle I92tconnected respectively to' the main toggle pivot H and to a fixed pivot2|, and a coacting latch 22. The latch 22 which is rotatably mounted at23 is adapted to engage a roller 24 carried by an extension 26 of thetoggle .45 link 28. An extension IQ of the toggle link [9 coacting withthe fixed pivot 2! maintains the toggle in an underset position so thatwhen the latch 22 is moved out of restraining engagement with respect tothe roller 24, the toggle |9Zil 50 collapses under the thrust exerted atthe pivot I i. t The toggle 8-9 is no longer in thrust-transmittingposition and is free to collapse, permitting reverse movement of theoperating rod 5 under bias of spring 5' to the solid line positionshown. 55

The latch 22 can be controlled in any suitable manner, as by theconventional tripping solenoid 25 or by independent manual meansindicated at 26.

Fig. 2 illustrates the thrust-transmitting linkage in the restraining orclosed position with respect to the operating rod 5. In this positionthe knee joint ll of the toggle 89 is overset and engages a stop member21. The linkage is thereby eifectively locked in this position withrespect to opposing thrust tending torotate the lever l5counterclockwise as long as the toggle pivot H is held fixed by theabove-described tripping means. When the tripping means is actuated inthe manner above indicated the tripping toggle l9-20 is no longerrestrained by the latch 22 and buckles, permitting the toggle pivot l lto move about the fixed pivot l3 in a counterclockwise direction underthe influence of the reacting forces tending to cause opening movementof the breaker rod 5. When the toggle 89 has collapsed and the lever 15rotated counterclockwise to the initial position shown in Fig. 1 whereinthe roller l0 again engages the operating face or low point of the cam,the tripping toggle Iii-28 is again stretched and extended so that theroller 24 rides beneath the latch 22. In this position: the mechanism isreset and in readiness for another cam operation.

The motor control system generally indicated at 28 is adapted todeenergize automatically the motor after a working stroke of the cam andto prevent a subsequent operation in the absence of a further positivecontrol operation by the operative. This control system per se forms nopart of the present invention and is described and claimed in aco-pending application of Carl Thumim and Thellwell R. Coggeshall,Serial No. 59,080, filed January 14, 1936 for Motor control system.

The control system comprises a control source of power indicated at 29from which the motor I is energized through a motor contactor 30. Themotor contactor operating coil 3| is adapted to be energized thrugh theoperatives switch 32 and a limit switch at 33. Accordingly, in order toinitiate energization of the motor the operative closes the switch 32thereby causing closing of the motor contactor 30. This operation sealsthe circuit of the contactor coil through auxiliary contacts at 34 in sofar as the operatives switch is concerned, so that the motor will not bedeenergized in the middle of the operating stroke by opening of theswitch at 32.

The motor is automatically deenergized at the end of the stroke by meansof a member 35 secured to the cam shaft 3. The member 35 is providedwith a pin .36 which picks up a loosely pivorted arm 31. At the end ofthe stroke. the member 37 lifts the pivoted switch member 38 so as toopen the motor contactor coil switch at 33, thereby opening the motorcontactor. At the same time the auxiliary switch at 39 is closed,thereby energizing the coil 40 in the event that the operatives switch32 is held closed. The switch member 38 is accordingly held in thatposition through the coacting armature 43-. It is therefore necessarythat the operative open the switch 32 and again close the same beforeanother operation can be initiated. Repeated operations o-r pumping ofthe mechanism is thereby precluded.

For most efficient operation of a cam, it is clear that the maximum.amount of useful dwell be gainfully employed, i. e., the low regionshould be limited to a minimum.

Due to inertia of moving parts, a certain amount of over-travel isunavoidable. The amount of over-travel permitted determines the extentof the low region.

Various means have been employed for limiting over-travel such asmechanical and electrical braking means, but these are attended by thehazard of straining working parts and by an indeterminate final camposition that is due to un'- avoidable operation of the control motor onvarying voltages. This results in varying amounts of kinetic energyrequiring dissipation after deenergization of the motor.

The present invention discloses a new means for causing the cam to cometo rest at approximately the same position after motor cut-01f,irrespective of the speed of the motor and momentum of the moving parts,thus permitting the low or ineffective portion of the cam. periphery tobe reduced to a working minimum.

The operating movement of the cam 4 is such that the high point of thecam clears the roller l0 when the toggle 89 moves to its over-setposition illustrated by Fig. 2. If the cam were instantly stopped atthat point roller l0 could en gage the low point of the cam immediatelyupon tripping so that the tripping means would immediately reset. 7

Assuming, however, that the roller it! drops to an intermediate point onthe cam. face, the tripping means cannot be reset until a partialrevolution of the cam is effected. However, there is present thepractical difficulty of synchronizing the speed of rotation of the camwith the toggle resetting operation so that when the low point of thecam passes under the main toggle roller III, the tripping means at 1resets without fail.

This might be accomplished safely by designing the cam with a low pointdwell period of but such cam design is obviously unsatisfactory as but180 remain for the working face.

For centering the cam prior to an operating stroke so as to insureresetting of the tripping means at a predetermined point on the cam andfor conserving the maximum efiective "dwell duration of the cam, therotating structure is permitted to over-travel even to the extent ofseveral revolutions, and means are provided for gradually and safelydissipating the kinetic energy and for returning this energy in part tothe cam for restoring it to a predetermined position.

To this end the cam shaft 3 is operatively connected to spring structure4! adapted to be tensioned when the cam 4 passes the predeterminedposition above referred to. Specifically, a pair of springs 42 aremounted on guide rods 43 between a pair of cross-heads 44 and 45. Thecross-head 44 is guided on the rods 43 and is connected through a crank46 and gears 41 and 48 to the cam shaft 3. The cross-head 45 ispivotally mounted at 49 for permitting oscillatory movement of theopposite end of the spring structure.

It will be noted that the gear 48, which is fixed to the shaft 3,operates through the gear 41 the movable cross-head 44 in piston mannerto compress the springs 42 when the cam rotates beyond the positionshown. Assuming noW that the cam rotates 45 degrees beyond the positionshown before the kinetic energy in the rotating structure is dissipated,the energy stored in the springs 42 acting through the cross-head 44 nowrotates the shaft gear 48 in the opposite direction so as to return andcenter the cam. In order to insure proper positioning of the cam underall conditions the gear 41 is provided with twice as many teeth as thegear 48 so that regardless of whether crank 455 stops at its upper orlower center position the cam 4 always stops at the proper position.

By insuring a predetermined starting position for the cam, a uniformoperating time is possible as well as high speed operation of the camdue to the fact that the tripping means is already reset.

Fig. 3 illustrates the same principle of cam resetting, except in thiscase a tension spring 50 is directly connected to an end of the shaft 3through an arm 5|. The spring 50, as in the case of the springs 42,opposes movement of the cam 4 beyond the predetermined starting positionand tends to restore the cam to its centered position after the kineticenergy is dissipated. However, it will be noted that it is possible forthe spring 50 to assume a dead center position when the shaft is 180degrees from the position shown. For overcoming this, an auxiliaryswitch 52 controlled by the member 5! is provided for giving the motormomentary energization from the source 29 so as to move the shaft offdead center. A resistance 53 is preferably provided in the auxiliarycircuit for insuring slow operation of the motor from this position.

It should be understood that my invention is not limited to specificdetails or construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artwithout departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Operating mechanism comprising a motor, a rotatable cam driventhereby, means adapted to be actuated from one position to anotherposition by said cam, said cam at the initiation of said operation beingin a preferred predetermined position with respect to said actuatedmeans, means for deenergizing said motor upon completion of said camoperation, and centering means for restoring said cam tosaid initialpredetermined position upon over-travel thereof.

2. Operating mechanism comprising a motor, a rotatable cam driventhereby, means adapted to be actuated from one position to anotherposition by said cam, said cam being in a predetermined angular positionwith respect to said actuated means at the initiation of said operation,means for deenergizing said motor upon completion of said cam operation,and means including spring structure for dissipating the kinetic energyin said operating mechanism after said deenergizing operation and forrestoring said cam to said initial predetermined position.

3. Operating mechanism comprising a motor, a rotatable cam driventhereby, collapsible thrusttransmitting structure adapted to be actuatedthrough an operating stroke by said cam, tripping means associated withsaid thrust-transmitting structure, said cam being in a predeterminedangular position with respect to said structure at the beginning of saidstroke for permitting resetting of said tripping means, means fordeenergizing said motor at the end of said stroke, and means fordissipating the kinetic energy stored in said operating mechanism whensaid motor is deenergized and for restoring said cam to saidpredetermined angular position prior to a subsequent operating stroke.

4. Operating mechanism comprising a motor, a rotatable cam driventhereby, collapsible thrust-transmitting structure adapted tobe actuatedthrough an operating stroke by said cam, tripping means associated withsaid thrusttransmitting structure, said cam being in a. .pre-

determined angular position corresponding to' the reset position of saidstructure at the beginning of said stroke, means for deenergizing saidmotor at the end of said stroke, and means including a spring adapted tobe tensioned in accordance with rotation of said cam beyond saidpredetermined angular position upon deenergization of said motor forreturning said cam to said position.

5. Operating mechanism comprising a motor, a rotatable cam driventhereby, collapsible thrust-transmitting structure adapted to beactuated through an operating stroke by said cam, tripping meansassociated with said thrusttransmitting structure, said cam being in apredetermined angular position with respect to said structure at thebeginning of said stroke, means for deenergizing said motor at the endof said stroke, said tripping means being adapted toreset for holdingsaid structure in thrust-transe mitting position when said cam is insaid prede-' termined angular position, and means including a springtending to center said cam with respect to said position.

6. Operating mechanism comprising a motor, a rotatable cam driventhereby, a thrust-transmitting linkageincluding a roller coacting withsaid cam, tripping means for holding said linkage in thrust-transmittingposition, said tripping means being adapted to reset when said cam is ina predetermined angular position with respect to said roller, rotationof said cam by said motor causing an operating stroke of said linkage,means for deenergizing said motor at the end of said stroke, and meansfor dissipating the kinetic energy stored in said operating mechanismand centering said cam with respect to said predetermined angularposition comprising a spring adapted to be tensioned to an extentcorresponding approximately to the over-travel of said cam with respectto said angular position.

'7. Operating mechanism comprising a motor, a rotatable cam driventhereby, means adapted to be actuated through an operating stroke bysaid cam, said cam at the initiation of said stroke respect to saidmeans, and means including spring structure adapted to be tensioned inac- I cordance with over-travel of said cam with respect to said angularposition upon completion of said operating stroke tending to center saidcam with respect to said position, said spring structure beingoperatively connected to said cam through ratio gearing for insuringcentering of said cam at a dead center position between said springstructure and cam.

8. Operating mechanism comprising a motor, a rotatable cam driventhereby, means adapted to be actuated through an operating stroke bysaid cam, said cam at the initiation of said stroke being in apredetermined angular position with respect to said means, and means forcentering said cam with respect to said angular position comprisingspring structure, said spring structure being fixed at one end, a crankoperatively connected to the other end of said spring structure, a gearconnected to said crank and a c0- actingtgear operatively connected tosaid cam,

the number of teeth of said first-named gear being a multiple of thenumber of those of said coacting gear for insuring centering of said camat a dead center position between said spring structure and cam.

9. Operating mechanism comprising a motor, a cam driven thereby, meansadapted to be actuated through an operating stroke by said cam, said camat the initiation of said stroke being in a predetermined angularposition with respect to said means, a springv operatively connected tosaid cam for opposing movement beyond said angular position therebytending to centersaid cam after. an operating stroke, and an auxiliary

